Circuit-breaker.



N0. 656,68l. I Patented Aug: 28, I900.

E. THOMSON.

CIRCUIT BREAKER.

(Application filed June 12, 1899.)

(No llodei.)

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NITE' STATES PATENT FFICE.

ELIHU THOMSON, OF SWAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO THE GENERALELECTRIC COMPANY, OF NEW YORK.

CIRCUIT-BREAKER.-

SPECIFICATION forming part of Letters Patent No. 656,681, dated August28, 1900.

Application filed June 12, 1899. Serial No. 720,295. (No model.)

To ail whom it may concern.-

Be it known that I, ELIHU THOMSON, a citizen of the United States,residing at Swampscott,county of Essex, State of Massachusetts, haveinvented certain new and .useful Improvements in Circuit-Breakers, (CaseNo. 1,216,) of which the following is a specification. This inventionrelates to safety devices for alternating-current systems, the objectbeing to protect translating or consumption devices upon a breaking downof their insulation.

The invention is particularly directed to the protection of transformersand the interruption of the supply-circuit upon failure of the transformer-insulation or extraordinary leakage in the secondary circuit.

In carrying out my invention I provide in the supply-circuit of thetransformer or consumption device a thermal or other cut-out and cause aheavy current sufficient to fuse or operate the same to flow when aleakage or ground branch of the consumption device is energized by afailure of insulation. I provide between the cut-out and the transformera short circuit normally open at a spark-gap, through which theline-current may flow when an arc is sprung and provide means forbreaking down the gap when the transformerdnsulation gives way or whenfor any reason there is an extraordinary increase of energy in thesecondary system. The leakage-current by which the cut-out is controlledmay be, for example, from a grounded sheath or conductor between theprimary and secondary transformer windings or from a ground to thetransformer-casing or from the secondary mains, the result being in anycase that upon the breaking down of the insulation sufficient currentwill leak to ground to close the short circuit through the spark-gap andactuate the thermal cut-out and interrupt the circuit.

My invention therefore in one of its aspects comprises adistribution-circuit for alternating currents, including a consumptiondevice fed through a thermal cut-out and means for operating saidcut-out upon the energization of a ground branch controlled by a ruptureof insulation of the consumption device.

The invention further comprises a distribution-circuit including atransformer and a cut out in the main or primary circuit thereof,depending for its operation upon the energization of a ground branchcontrolled by the condition of the insulation of the transformer or bythe potential of its secondary circuit and controlling in turn a shortcircuit of the primary mains through the cut-out.

The invention also comprises other and more specific features, whichwill be hereinafter more fully described, and will be delinitelyindicated in the claims.

In the drawings, Figure 1 is a diagram showing a cut-out operated by thegrounded sheath of the transformer. Fig. 2 shows a system in which thecontrolling ground connection is taken from one side of the secondary.In Fig. 3 the ground connection is taken from the neutral wire of athree-wire system. In Fig. 4 the ground connection is made with thetransformer frame or casing.

Referring to the drawings, 1 2 represent the primary leads of atransformer or the supply-leads of a consumption device of othercharacter.

3 represents the primary winding of the transformer, the secondary ofwhich feeds a lamp or other consumption circuit 4:.

5 represents what is known in the art as a ground-shield, being a copperseparating medium between the two transformer-windings provided with anearth connection. In this connection I interpose the primary of a smallauxiliary transformer 6, the secondary of which controls the operationof a thermal cut-out '7 7. (Shown specifically as fusewires.) To preventthe reaction of the secondary winding of the transformer 6 upon the lineand permit easy flow of current when the protective device acts, Idifferentially connect the windings, so thatlike terminalsthat is tosay, those which are in the same inductive relation to thetransformer-coreconnect with opposite mains of the supplycircuit. Inorder to prevent the secondary circuit of this auxiliary transformerfrom normally short-circuiting the main supply-circuit of theconsumption device or main transformer, I interpose between the maincircuitleads 1 2 and the said secondary circuit spark gaps S 8,consisting of metallic terminals separated by an air-space or by a thinfilm or stratum of insulating material adapted to break down upon adefinite increase of potential. The sparking devices are connectedthrough a condenser 0. The parts may with advantage be arranged as shownin the diagram, the connections from the main circuit leading to a pointbetween the spark-gaps and the condenser-terminals and the middle pointof the differential winding on the secondary of the auxiliarytransformer (3 being connected with an intermediate part of thecondenser. he condenser is of comparatively-small capacity. Its leavesare provided with three terminals, two connecting with the mains and thethird with the junction of the differential transformer coils. Theauxiliary transformer should preferably be step-up in character, thenumber of turns being such as to admit of a small reactance. As thusorganized it will be seen that upon the breaking down of the insulationof the transformer part of the primary current will leak through thegrounded sheath 5 and react inductively upon the auxiliary transformer6, thereby breaking down the insulating-film in the spark-gaps andexciting the condenser O rhythmically with the line-rate. The bridgingof the spark-gaps permits a heavy current to be drawn through thefusible cut-outs 7 7, causing their fusion and the opening of thecircuit.

In Fig. 2 an organization somewhat similar to that which has just beendescribed is depicted, except that herein the auxiliary transformer 6 isprovided with independent magnetic circuits for the two secondarysections, which are diiferentially connected and discharge into theline-terminals through the common connection 10. This arrangement is notso satisfactory, as the separate magnetic circuits produce a largerreactance than a superposed winding. In this diagram I show thesecondary circuit as connected with the ground or leakage branch. Itfollows in this case also that if the insulation of the transformerbreak down the secondary circuit will be charged with extraordinarypotential and will cause the primary fuse or thermal cutouts to act inthe same manner as described in connection with Fig. 1.

In Fig. 3 the relationship of the parts is the same as in Fig. 1, exceptthat the secondary is shown as a three-wire system, the middle wirebeing connected in the ground branch which controls the automaticcut-out.

In Fig. 4 the organization differs from that shown in Fig. 1 in that thetransformer frame or casing is connected in the ground or leakage branchinstead of the grounded sheath between the two windings.

It will be evident that my invention may be applied to various types ofelectrical devices for transferring, translating, orconsumin g electricenergy, and I refer to such gener ically in the claims by thecomprehensive term translating device.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is

I. In a system of altemating-current distribution, the combination oftwo circuits insulated from one another, one including a source ofcurrent and the other consumption devices, a thermal cut-out in thesupply-circuit, and a magnetic operating device determining theoperation of the cut-out actuated upon failure of the insulation.

2. In a system of alternating-current distribution, the combination of atransformer the primary circuit of which includes a thermal cut-out andthe secondary translating devices, a leakage branch, and magnetic meanscontrolled thereby to admit an operating current through the cutout-.

3. In a system of alternating-current distribution, the combination of atransformer, the primary of which includes a thermal cutout, and thesecondary translating devices, a leakage branch, and magnetic meanscontrolled thereby to admit an operating-current through the cut-outupon extraordinary rise of potential in the secondary system.

at. In a system of alternating-current distribution, the combination ofa transformer, the primary of which includes a thermal cutout, a leakagebranch from the transformer fed with current upon a failure ofinsulation, an auxiliary transformer having its primary in said branchand its secondary controlling the cut-out.

5. In a system of alternating-current distribution, the combination of atransformer, the primary of which includes a thermal cutout, a leakagebranch from the transformer rendered active upon a failure ofinsulation, an auxiliary transformer having its primary in said branchand its secondary adapted to short-circuit the primary mains of thecut-out.

6. The combination with a translating device of a ground branch normallycompleted from a metallic part of said device but insulated from thesupply-circuit adapted to be energized upon a failure of insulation insaid device, and a current-interrupter controlled by said branch.

7. The combination with a translating device, of a leakage branch forcurrent operating upon the failure of insulation in the said device, atransformer fed by such leakageeurrents, the secondary winding of whichis connected with the supply-circuit through a spark-gap and controllinga thermal cut-out in the supply-circuit.

8. The combination with a translating device, of a ground branchprotecting the same, energized upon a breaking down of the insulation, atransformer having its primary-in said branch, and a split secondarydifferentially connected with the supply-circuit to neutralize theeffect of the several sections upon said circuit, a spark-gap betweenthe transformer secondary and the supply-circuit, and a thermal cut-outin the supply-circuit controlled by said secondary.

9. The combination with a translating device, of a ground branchenergized upon a failure of insulation in said device, a circuitbreakerin the supply-circuit,and a spark-gap in a branch of the supply-circuitcontrolled by said ground branc 10. The combination with a translatingdevice, of a ground branch protecting the same and adapted to beenergized upon a failure of the insulation in the device, a transformercontrolled by said ground branch, and a circuit interrupter actuated bysaid transformer.

11. The combination with a translating device, of a branch connectionopen at a point closely related to its winding so as to complete a leakupon rupture of the insulation, and a circuit-interrupter for thesupply-circuit operated by said branch.

12. The combination with a translating device, of a branch connectionopen at a point closely related to its winding so as to complete a leakupon rupture of the insulation, a thermal cut-out in the supply-circuit,and means controlled by the branch when energized to direct anoperating-current through the cut-out.

13. The combination with a translating device, of a branch connectionopen at a point closely related to its winding so as to complete a leakupon rupture of the insulation, a fuse in the supply-circuit, and meansfor directing current through the fuse sufficient to blow it when thebranch is energized.-

14. The combination with a translating device, of a branch connectionopen at a point closely related to its winding so as to complete a leakupon rupture of the insulation, a circuit-interrupter in thesupply-circuit operating upon determinate increased current-flow, ashortcircuitincludingsaidinterrupteranda spark-gap, an electromotive devicecontrolled by the leak branch for bridging the sparkgap, and a condenseraround the spark-gap.

15. In an alternating-current system, the combination of asupply-circuit, consumption devices inductively fed thereby, a cutout,and a circuit controlling its operation energized on a failure ofinsulation between the supply-circuit and the circuit including theconsumption devices.

16. In an alternating-current system, the combination of a supplycircuit, a transformer connectedtherewith, a cut-out controlled by acircuit including a spark-gap, a differential transformer feeding thesparkgap, and means for energizing the difierential transformer upon afailure of insulation of the distributing-transformer.

In Witness whereof I have hereunto set my hand this 9th day of June,1899.

ELIHU THOMSON.

Witnesses:

DUGALD MQKILLOP, HENRY .0. WESTENDARP.

